Protestant orange march celebrations have often been marred by clashes.

At least 27 police officers have been injured in Northern Ireland, including three who were hit by gunshot pellets, during an overnight riot, reports say.

Missiles were thrown and petrol bombs ignited in clashes between Catholics and Protestants ahead of the biggest day of Northern Ireland's marching season, AFP reported.

"This is utterly wrong and I condemn it in the strongest possible terms," said Chief Superintendent Mark Hamilton of the Police Service of Northern Ireland.

"These officers were doing their jobs, were policing their local community and have been attacked whilst doing so."

Hamilton criticized those involved in the riots as having intentions to cause "mayhem and destruction."

Protestant Orangeman march, also called "The Twelfth," is celebrated by Protestants in Northern Ireland as they mark the victory of Prince Williams of Orange over the Catholic King James II at the Battle of Boyne in 1690.

Despite a 1998 peace agreement, Northern Ireland is still subject to violent outbreaks around July 12, as Catholics oppose the marches and prevent them from taking place.